The present invention relates to an apparatus for recording and reproducing a digital video signal, and more particularly to a circuit configuration which is used for recording and reproducing a digital video signal in both a standard mode and a long playing mode and is suitable for use in various recording/reproducing apparatuses different in hierarchy from each other.
A digital VTR (namely, digital video tape recorder) for recording and reproducing a video signal in the form of a digital signal is known. That is, a digital VTR for recording a PCM signal which is obtained by performing a sampling operation for a video signal in such a manner that a Nyquist condition is satisfied, directly on a tape, is described in an article entitled "Digital Video Recording Techniques using 1/2 inch Metal Particle Tape" by S. Mita et al. (IEEE Consumer Electronics, Aug. 1985, pages 386 to 397).
Further, a digital VTR for compressing the above-mentioned PCM signal by the high-efficiency coding techniques using Hadamard transformation, to elongate the recording/reproducing time per unit length of a recording tape, is disclosed in an article entitled "High Density Recording and Bit Rate Reduction for a 2-hour Digital VTR" by C. Yamamitsu et al. (Video Audio & Data Recording, Mar. 1986, pages 113 to 120).
It is desirable that a digital VTR can record and reproduce a video signal in both a standard mode and a long playing mode as in a home-use analog VTR which adopts one of the Beta-and VHS-methods and uses a 1/2 inch cassette tape.
In the digital VTR disclosed in the above article, however, the PCM signal used in the standard mode and the signal which is obtained by compressing the PCM signal by the high-efficiency coding techniques using Hadamard transformation and is used in the long playing mode, are utterly different in signal form from each other. Hence, in order to record and reproduce a video signal in both the standard mode and the long playing mode by the digital VTR, the digital VTR is required to have a signal processing circuit for the standard mode and another signal processing circuit for the long playing mode. Thus, the VTR is complicated in circuit construction, and becomes high in manufacturing cost.